The present invention relates to a new and uniquely constructed rasp blade for use in tire buffing machines to properly precondition tires in preparation for retreading. More particularly, the present invention relates to a tire rasp blade having a novel geometry and construction of the blade's working edge such that a greater number of teeth may be employed in a particular blade while retaining adequate tooth size, thus achieving maximum cutting efficiency, a longer useful life and other enhanced performance characteristics.
Tire rasp blades have been used for many years in the tire retreading industry. These blades are mounted to the rotating hub of the tire buffing machine and, when engaged with the used tire carcass, they cut or shear segments of rubber from the tread surface area of the tire. In this way, the tire is "buffed" to remove the unwanted used tread and to achieve an evenly textured surface suitable for retreading.
There are several distinct performance characteristics that are important to the successful operation and use of such tire rasp blades. The speed or efficiency of rubber removal during the tire buffing process is very important; by removing the unwanted rubber tread from the tire more quickly, the labor cost associated with the retreading process is reduced. It is also essential, however, that the tire rasp blade exhibit good durability--that is, the teeth positioned on the blade should not bend, break, wear or otherwise fail prematurely. It is also important that the blade not generate excessive heat during the buffing operation, since the tire surface can be damaged or even burned by increased temperatures with the result that an effective retread is not possible. Other important performance characteristics include the efficient utilization of energy and the generation of relatively low noise levels during operation. Finally, it is also very important that the tire rasp blade leave a certain well-defined texture on the surface of the tire carcass from which the unwanted rubber has been removed. Too rough a surface will result in a poor bond between the tire carcass and the new tread, thereby causing premature failure of the retreaded tire.
A number of prior art tire rasp blades have been developed in an attempt to meet the performance characteristics noted above. Such rasp blades are disclosed, for example, in U.S. Pat. Nos. 3,879,825; 4,021,899; 4,091,516; and 4,283,819. Another tire rasp blade construction, representing an improvement over these prior art structures, is disclosed in my U.S. patent application Ser. No. 07/166,176, filed Mar. 10, 1988. There still exists a need, however, for an economically produced tire rasp blade with excellent durability that removes rubber from the tire carcass at a faster rate, while providing an excellent surface texture on the buffed tire, and while maintaining relatively lower buffing temperatures.
There is also a present need in the tire retreading trade for a more durable, yet efficient tire rasp blade for use with both flat-faced and curved-face buffing hubs. The durability of the tire rasp blade used in curved-face buffing hubs is particularly important because fewer numbers of blades contact the tire at any one time during the operation of the curved-face hub, as compared to flat-faced hubs. Because a curved-faced buffing hub offers certain advantages over flat-faced hubs, a more durable, high performance blade for use in curved-faced hubs would make these hubs more attractive as alternatives to flat-faced hub assemblies.